According to the skilled in the art, linear compressors comprise at least one arrangement wherein the piston is functionally associated with a linear electrical engine, wherein the objective of this arrangement consists of axially moving the piston in the interior of a cylinder, promoting the compression of a working fluid.
Thus, the skilled in the art already known linear compressors based on resonant oscillating mechanisms, wherein the piston (which glides in the interior of a cylinder, promoting the compression of a working fluid) and the linear engine (fundamentally composed by a fixed stator and a movable magnet) have their motion dynamics defined by means of a body with resilient features and which is susceptible of resonant linear vibration (which comprises the attaching element between the piston and the magnet of the linear engine).
Some functional examples of linear compressors based on resonant oscillating mechanisms are described in document BRPI0601645. One of these functional examples comprises a compressor wherein the magnet of the linear engine is attached to the piston by means of a resilient element as a resonant helical spring, wherein said piston (together with corresponding attaching elements thereof) is arranged in one of the ends of the resilient element, while the magnet (together with corresponding attaching elements thereof) is arranged in its opposed end. This arrangement enables that the movement between the opposed ends of the resilient element presents a difference of 180° (a hundred and eighty degrees). In this arrangement, the resilient element further presents a region in which the axial oscillation (or axial movement) tends to zero, wherein said region—which comprises all the region located the springs of the resilient element (or resonant spring)—is known as neutral point. Furthermore, in accordance with document BRPI0601645, the mechanical attachment between the external shell of the compressor (normally cylindrical and tubular) and the resilient element shall be effectuated through said neutral point, aiming not modifying the oscillation conditions of the already mentioned elastic element.
Although the concepts and constructiveness observed in document BRPI0601645 meet all the intended objectives (in ideal operating situations), it shall be noted the lack of axial stiffness necessary for maintaining the positioning of the resonant oscillating mechanism in the interior of the shell in situations wherein it is noted the unbalance of mass or stiffness (neutral point with oscillation different from zero), which may occur due to several reasons (non-ideal situations).
To overcome this unfavorable aspect, the current state of the art further provides an arrangement of linear compressor (based on a resonant oscillating mechanism) wherein it is included an intermediate element among the compressor shell and the resilient element.
This arrangement including an intermediate element is defined, in detail, in the Brazilian document No. BRPI1005184 of Dec. 27, 2010, which is also applied to the same author of the present application.
Thus, it is defined an intermediate element composed by an integrated tubular body, at least a group of rips (which defines an axially flexible surface), and at least one attaching point for the resilient element or resonant spring. Specifically, it is provided two symmetrically-arranged attaching points, wherein each one of the attaching points comprises a thru hole defined in the axially flexible surface. According to said document, the intermediate element is arranged in the interior of the compressor shell, and the resonant spring is arranged in the interior of the intermediate element. This arrangement is fixed with bolts and similar tools, which pass through the axially flexible surface of the intermediate element and the neutral point of the resonant spring.
The Brazilian document No. BRPI1005184 further discloses the presence of flat leaf springs assembled together with the side faces of the intermediate element. Said flat springs have the function of increasing the transverse stiffness between the resonant oscillating assembly and the compressor shell and further guaranteeing that occasional concentricity errors (of the resonant oscillating assembly) will be reduced.
If said flat leaf springs do not have an angular indexing related to the resilient element that connects the magnet to the piston, the transverse vibration of the compressor, measured in two transverse directions, one direction on the base plan of the compressor (bottom) orthogonally to the direction of the piston motion and the other direction on the vertical plan orthogonally to the piston motion, will also have a variability that will follow the position of spring legs. Considering the indexing, the forces transmitted to the shell by the spring legs will have a fixed position. Consequently, the vibration caused by said forces will have a lower variability.
The lack of indexing can also result in a concurrence (coincidence) between the frequencies of some vibration modes and some harmonicas of functioning, resulting in the increase of compressor vibration, or even its non-operation.
In view of the foregoing, it remains obvious the need of developing a linear compressor based on a resonant oscillating mechanism not containing the disadvantages described above.